V 0 A 2017 DownSyndrome 1 Down Syndrome

V 0 A 2017 -Down-Syndrome 1 Down Syndrome by Birth Order & Mom’s Age by Milo Schield Member: International Statistical Institute US Rep: International Statistical Literacy Project Director, W. M. Keck Statistical Literacy Project Slides and Data at: www. Stat. Lit. org/ pdf/2017 -Schield-Downs-Syndrome-Slides. pdf xls/2017 -Schield-Downs-Syndrome-Data. xlsx

V 0 A 2017 -Down-Syndrome 2 Down Syndrome Each person has 23 chromosome pairs. Chromosomes are small “packages” of genes. Down syndrome is a defect in chromosome 21. Down syndrome is a genetic defect. It is not the most common genetic defect. It is #3 after cystic fibrosis & Huntington’s disease. About 6, 000 US babies/year have Down syndrome.

V 0 A 2017 -Down-Syndrome Down Syndrome Kids. 3

V 0 A 2017 -Down-Syndrome 4 Down Syndrome: Common Health Problems • • Hearing loss (up to 75%) Obstructive sleep apnea (between 50 -75%) Ear infections (between 50 -70%) Eye diseases like cataracts (up to 60%) Heart defects present at birth (50%) Disease: Symptoms with a definite cause. Syndrome: Symptoms without a definite cause. Usage may linger after cause is identified.

V 0 A 2017 -Down-Syndrome Down Syndrome Kids. 5

V 0 A 2017 -Down-Syndrome Down Syndrome Adults: Intelligence & Behavior Average IQ of Down syndrome adult: 50: the mental ability of a 9 -year-old Down syndrome kids: slower to speak. Down-syndrome child-behavior problems: • negativity, impulsivity, • oppositional behavior, inattention, • noncompliance, and disobedience, especially as they get older. 6

V 0 A 2017 -Down-Syndrome Some Down Syndrome Kids Excel Actors: Chris Burke played Corky in Life Goes On Lauren Potter plays Becky Jackson on Glee 7

V 0 A 2017 -Down-Syndrome 8 Average Survival Age and Sex Ratio Due to advances in medical technology, individuals with Down syndrome are living longer. • Before antibiotics, average survival age was nine. • With antibiotics, average survival age was 19. • With antibiotics and corrective heart surgery, 80% of adults with Down syndrome reach age 60. Among infants with Down syndrome, males are 24% more prevalent than females. Among moms 20 -24, the male-female sex ratio is 1. 73. The sex-ratio decreases as the age of the mother increases.

V 0 A 2017 -Down-Syndrome Down Syndrome Rate by Birth Order. 9

V 0 A 2017 -Down-Syndrome Down Syndrome Rate by Mom’s Age. 10

V 0 A 2017 -Down-Syndrome Down Syndrome Rates: Combine into Two Groups Combine birth orders into two groups. Combine mom’s ages into two groups. Conceptually simpler. Facilitates simple arithmetic comparisons. Check conditions for Simpson’s paradox 11

V 0 A 2017 -Down-Syndrome Down Syndrome Rate by Birth Order and Mom’s Age Later children are twice as likely to have Down syndrome as [are] earlier children. Older moms are seven times as likely to have Down syndrome child as [are] younger moms. 12

V 0 A 2017 -Down-Syndrome 13 Down Syndrome Rate by Birth Order and Mom’s Age Later children are 112% more likely to have Down syndrome than [are] earlier children. Among younger moms, later children are 14% more likely to have Down syndrome than earlier children. Among older moms, later children are 16% more likely to have Down Syndrome than earlier children.

V 0 A 2017 -Down-Syndrome 14 Down Syndrome Rate: Controlling for Moms Age Before controlling for Mom’s age, “Later children are 112% more likely to have Down syndrome than earlier children [more than twice as likely as earlier children]. After controlling for mom’s age, “Later children are 14 to 16% more likely to have Down syndrome than earlier children.

V 0 A 2017 -Down-Syndrome 15 Down Syndrome Cases: Association between birth order and mom’s age. Earlier children: more likely to have younger moms. Later children: more likely to have older moms. Mom’s age confounds influence of birth order on chance of a child having Down syndrome.

V 0 A 2017 -Down-Syndrome Down Syndrome Rate by Birth Order and Mom’s Age. 16

V 0 A 2017 -Down-Syndrome Down Syndrome: Most Common vs. Most Likely 54% of children with Down syndrome are born to women under 35 years of age. Children with Down syndrome are most common for Moms under 35 years old. Children with Down syndrome are most likely for Moms over 35 years old. 17

V 0 A 2017 -Down-Syndrome 18 Conclusion Being a statistician involves searching for the strongest – the most fundamental – factors that influence an association. Ignoring stronger factors can lead to Simpson’s paradox or simply misunderstanding the relevant statistical associations that might better serve as a basis for identifying causal connections.